Surface diffusion of tungsten adatoms induced by low-energy bombardment with He atoms

Using low-temperature field ion microscope techniques, we studied at the atomic level the elementary events of radiation-induced surface diffusion of tungsten adatoms on the ideally pristine surface. The experiments on surface-damage formation and adatom displacements have been performed in situ with a source of neutral helium atoms with an energy of 5?keV. It was demonstrated that the low-energy He atomic bombardment at grazing incidence was able to induce a substantial surface mobility of adatoms. Most of the radiation-induced adatom displacements were oriented along the direction of irradiation. The long impact-induced jumps of adatoms, spanning more than a nearest-neighbor distance, were revealed. Performed molecular dynamics simulations reproduce the general experimental trends and conclusions.     

Photochemical activities of polymers with aurone fragment

ABSTRACT

In this work we report preliminary results obtained for methacrylic polymers incorporating aurone side-group as photochemical active molecule. The aurone polymers were obtained by a three-step synthetic approach: (2Z)-6-hydroxy-2-(4-R-benzyliden)-1-benzofuran-3(2H)-ones were synthesized by using condensation reation of 6-hydroxybenzofuran-3-one with benzaldehydes; then methacrylate monomers were synthesized by reaction the alcohols with methacryloyl chloride; and the polymers were synthesized by free radical polymerization. Polymers were characterized by ¹HNMR spectroscopy and DSC techniques. Their physicochemical properties are determined by absorption, fluorescence excitation and emission spectroscopies.     

Generations of Monic Polynomials such that the Coefficients of Each Polynomial of the Next Generation Coincide with the Zeros of a Polynomial of the Current Generation,and New Solvable Many-Body Problems

The notion of generations of monic polynomials such that the coefficients of each polynomial of the next generation coincide with the zeros of a polynomial of the current generation is introduced, and its relevance to the identification of endless sequences of new solvable many-body problems “of goldfish type” is demonstrated.     

Approximation of Fractional Brownian Motion by Martingales

We study the problem of optimal approximation of a fractional Brownian motion by martingales. We prove that there exists a unique martingale closest to fractional Brownian motion in a specific sense. It shown that this martingale has a specific form. Numerical results concerning the approximation problem are given.     

Highly sensitive detection of human cardiac myoglobin using a reverse sandwich immunoassay with a gold nanoparticle-enhanced surface plasmon resonance biosensor

A highly sensitive reverse sandwich immunoassay for the detection of human cardiac myoglobin (cMb) in serum was designed utilizing a gold nanoparticle (AuNP)-enhanced surface plasmon resonance (SPR) biosensor. First, a monoclonal anti-cMb antibody (Mab1) was covalently immobilized on the sensor surface. AuNPs were covalently conjugated to the second monoclonal anti-cMb antibody (Mab2) to form an immuno-gold reagent (Mab2-AuNP). The reverse sandwich immunoassay consists of two steps: (1) mixing the serum sample with Mab2-AuNP and incubation for the formation of cMb/Mab2-AuNP complexes and (2) sample injection over the sensor surface and evaluation of the Mab1/cMb/Mab2-AuNP complex formation, with the subsequent calculation of the cMb concentration in the serum. The biosensor signal was amplified approximately 30-fold compared with the direct reaction of cMb with Mab1 on the sensor surface. The limit of detection of cMb in a human blood serum sample was found to be as low as 10 pM (approx. 0.18 ng mL⁻¹), and the inter-assay coefficient of variation was less than 3%. Thus, the developed SPR-based reverse sandwich immunoassay has a sensitivity that is sufficient to measure cMb across a wide range of normal and pathological concentrations, allowing an adequate estimation of the disease severity and the monitoring of treatment.     

Laser flash photolysis study of electron transfer processes of adsorbed anthracene on titania–silica surfaces

We have studied the photophysics of anthracene adsorbed to photocatalytic silica–titania mixed oxide systems prepared by two different methods: a sol–gel synthesis and an impregnation route. The observed photophysics depend upon the method of synthesis, with the sol–gel prepared samples resulting in enhanced radical cation formation via static excited singlet state quenching. This mechanism, whilst operative, does not give rise to long-lived charge separation in the case of the impregnated samples. These results are discussed in terms of differing sample morphologies.     

Unimolecular reactions of CF2ClCFClCH2F and CF2ClCF2CH2Cl: observation of ClF interchange

The unimolecular reactions of CF(2)ClCFClCH(2)F and CF(2)ClCF(2)CH(2)Cl molecules formed with 87 and 91 kcal mol(-1), respectively, of vibrational energy from the recombination of CF(2)ClCFCl with CH(2)F and CF(2)ClCF(2) with CH(2)Cl at room temperature have been studied by the chemical activation technique. The 2,3- and 1,2-ClF interchange reactions compete with 2,3-ClH and 2,3-FH elimination reactions. The total unimolecular rate constant for CF(2)ClCF(2)CH(2)Cl is 0.54 +/- 0.15 x 10(4) s(-1) with branching fractions for 1,2-ClF interchange of 0.03 and 0.97 for 2,3-FH elimination. The total rate constant for CF(2)ClCFClCH(2)F is 1.35 +/- 0.39 x 10(4) s(-1) with branching fractions of 0.20 for 2,3-ClF interchange, 0.71 for 2,3-ClH elimination and 0.09 for 2,3-FH elimination; the products from 1,2-ClF interchange could be observed, but the rate constant was too small to be measured. The D(CH(2)F-CFClCF(2)Cl) and D(CH(2)Cl-CF(2)CF(2)Cl) were evaluated by calculations for some isodesmic reactions and isomerization energies of CF(3)CFClCH(2)Cl as 84 and 88 kcal mol(-1), respectively; these values give the average energies of formed molecules at 298 K as noted above. Density functional theory was used to assign vibrational frequencies and moments of inertia for the molecules and their transition states. These results were combined with statistical unimolecular reaction theory to assign threshold energies from the experimental rate constants for ClF interchange, ClH elimination and FH elimination. These assignments are compared with results from previous chemical activation experiments with CF(3)CFClCH(2)Cl, CF(3)CF(2)CH(3,) CF(3)CFClCH(3) and CF(2)ClCF(2)CH(3).